I live in a very, very rural part of the country. Land is CHEAP; you can buy 100+ acres of forest for under $2000/acre. There are a lot of vacant houses. Why? Because no one wants to live here. (Obviously not no one, since I chose to move here, but still.) There aren't jobs locally; part of the price I pay for living where I want to live is spending 3+ hours in a car commuting each day. The vacant houses are vacant because the people that lived there either died, or moved because they couldn't get work. They're not vacant because some venture capital real estate company is buying up rural homes just to hold on to them as they rot away.
The issue isn't vacant housing; the issue is where the housing is, and whether it's actually habitable or not.